Air blast circuit interrupter



Dec. 2o, 1949 R. E. FRINK 2,491,964

AIIR BLAST CIRCUIT INTERRUPTER Filed Aug. 22, 1946 WLTN EssEs: EINVENTOR 43 190556//5 f/kf j BY i 7LT/Town?! Patented Dec. 20,V 1949UNITED STATES PATENT OFFICE AIR BLAST CIRCUIT INTERRUPTER Russell Frink,Pittsburgh, Pa., assigner to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application August 22,1946, Serial No. 692,331

(Cl. 200e-148) 3Claims.

This invention relates to circuit interrupters in general, and moreparticularly to arcextinguishing structures therefor.

The interruption orlow currents with a mag-- netic type circuit breakerwithout unduly long arcing time has always been a problem. This islargely a question of getting the arc ofi from the arcing contacts andonto the arcing horns. 1t is generally known that this can be 'accomuplished by blowing a puff of air across the conu tacts, and when this isdone, speedy interruption results.

A general purpose of my invention is to provide an improved pneumaticmechanism which will accomplish the above, and vwhich will be simple andeconomical to manufacture.

A more specic object of my invention is to improvise an improved circuitinterrupter of the air break type in which a pivotally mounted switcharm carrying a pneumatic cylinder is rotated during the openingoperation, and a piston movable within the pneumatic cylinder is operuable to force a jet of air across the coacting arcingr contacts toassist in extinguishing the arc drawn thereat.

Another object is to provide an improved circuit interruptor of the airbreak type in which a puff of compressed air is more eiectively directedacross the separating contact structure during the opening operation.Preferably, the puff of air is created by pneumatic means including apneumatic cylinder secured to and movable with the pivotally mountedswitch arm.

Further objects and advantages will readily become apparent upon areading of the following specification, taken in conjunction with thedrawing, in which:

Figure 1 is a side elevational View, part1ally in section, of anair-break circuit breaker embodying my invention and shown in the closedc1rcu1t position; and

Fig. 2 is a modiiied type of circuit interrupter embodying my invention,and also shown in the closed circuit position.

Referring to the drawing, and more particularly to Figure 1 thereof, thereference numeral I designates a base which mounts insulator bushings2,`3, interiorly through which extend terminal studs 4, 5. The terminalstud 4 is preferably integrally ormed with a kconducting portion 6 whichsupports a relatively stationary contact assembly generally designatedby the reference numeral 1.

A pivotally Amounted switch arm 8 carries the movable contact structuregenerally designated 2 i by the reference numeral 9 and has its lowerend pivotally mounted at the fixed pivot I0 which 'is supported by aconducting portion I'I of the lower terminal stud 5. A main bridgingcontact I2 is carried by means of two studs I3, `I4 which pass throughthe switch arm 8 and have nuts I5 and It threadedly secured thereto.Preferably, compression springs il, I8 areprovided, disposed between thebridging contact I2 and the inner face of the switch arm 8 tobias the'main bridging contact I2 outwardly. The extremities of the bridgingcontact I2 make engagement with Axed main contacts i9, 2E! which areelectrically co`nnected respectively with terminal studs 4, 5.

The relatively stationary contact assembly 'I comprises a relativelyVstationary transfer 'contact 2l and a relatively stationary arcingcontact 22. The transfer contact 2`I, in the closed circuit position ofthe interrupte'r as shown in Fig. 1, makes engagement with a movabletransfer contact 23 carried by the switch arm 8. Cof acting with thestationary arcing contact 22 is a movable arcing contact 24 carried atthe outer free extremity of the switch arm 8.

From the foregoing description, it will be apparent that in the closedcircuit position of the interrupter shown in Fig. 1, the electricalcircuit therethrough includes terminal Istud 4, conducting portion E,main contact I9, bridging contact I2, fixed main contact 2U, to thelower terminal stud 5. During theopening operation, an oper ating rod 25composed of insulating material and pivotally connected at v2t to abracket 2 oi the switch arm 8 is moved downwardly by suitable mechanism(not shown), to cause clockwise opening rotative motion of the switcharm'.Y The contact opening sequence is as follows. First,'the bridgingcontact I2 separates from the fixed main contacts i9 and 2U, not beingsubjected thereby to any arcing whatsoever. Since the transfer contacts2l, 23 are electrically in parallel with the main contacts, the transfercontacts permit the current to pass therethrough. Further openingmovement causes separation of the transfer contacts 2 I, 23 to force thecurrent to pass through the arcing contacts 22, 2 4. Finally, the arcingcontacts 22., 24 separate to draw an arc therebetween.

It will be noted that a loop Icircuit is -formed including the terminalstuds 4, v5 and the switch arm 8. In any loop circuit, the'forces aresuch as to expand the loop. Consequently, the arc which is drawn at thearcing contacts 22,24, is bowed upwardly intolthe arc-extinguishingstructure generally designated by the reference numeral 2B. Thearc-extinguishing structure 28 may assume any desired form, butpreferably it is of the type set forth in United States patentapplication Serial No. 514,362 filed December 15, 1943, now U. S. Patent2,442,199, issued May 25, 1948, to Robert C. Dickinson and Russell E.Frink, and assigned to the assignee of the instant application.

The arc which is bowed upwardly into the arcextinguishing structure 28has its terminal ends transferred to the arcing horns 29, 30. Thetransfer of the left-hand terminal of the arc from the relativelystationary arcing contact 22 to the arcing horn 29 cuts into seriescircuit the blowout coil 3|. The energization of the blowout coil 3|creates a transverse magnetic field in the arcextinguishing structure 28to thereby effect upward movement of the arc to consequently effect theextinction of the same. The blowout coil 3| has a strap connection 32 tothe conducting portion 6 of terminal stud 4. The blowout coil 3| alsohas a strap connection 33 to the arcing horn 29. Thus, when the arc isdisposed within the arc-extinguishing structure 23, the electricalcircuit includes terminal stud 4, conducting portion 6, strap 32,blowout coil 3i, strap 33, arcing horn 29, the arc (not shown) disposedin the extinguishing structure 28, arcing horn 38, conducting strap 34,to the conducting portion 35 of the lower terminal stud 5.

During the interruption of high amperage currents, the interruptingability of the extinguishing structure 2B is sufficient to effect rapidtransfer of the are to the arc horns 29, and 33 and speedy interruptionof the high-amperage arc drawn therein, it being noted that at this timethere is an intense transverse magnetic field set up by the blowout coil3|. The same rapid interrupting ability is obtained during theinterruption of moderate currents. However, during the interruption oflow-amperage currents, the tendency of the current loop to cause the arcto expand and transfer to the arcing horns is practically nil, sincethis force is proportional to the square of the current. The result isthat the arc remains across the arcing contacts until enough thermalcurrents have been produced to accomplish the transfer. Also, after thetransfer is accomplished the transverse magnetic field set up by blowoutcoil 3l is relatively weak, and interruption is sluggish. The totaleffect may be arcing times of the order of thirty cycles or more forsome values of low-amperage currents.

To facilitate the interruption of such lowamperage current arcs, I haveprovided pneumatic means generally designated by the reference numeral36 and including a pneumatic cylinder 31, having lug portions 38 throughwhich extend bolts 39, thereby securing the pneumatic cylinder 31 to theswitch arm 8. Preferably the pneumatic cylinder 37 is of a lightweightmetal, such as aluminum, to minimize the mass of moving material. Arelatively short nozzle 48 permits communication from the upper end ofthe pneumatic cylinder 3l' to the region immediately adjacent to themovable arcing contact 24, the latter moving with the free end of theswitch arm 8.

Positioned within the cylinder 3l is a piston 4| secured to the upperend of a piston rod 42, the lower end of which is pivotally mounted at43 between a pair of outwardly jutting brackets 44 projecting from theconducting portion 35 of the lower terminal stud 5. Since the lower endof the piston rod 42 is pivotally connected to a fixed pivot 43,clockwise rotation of the switch arm 8 about the pivot I8, as caused bythe operating rod 25, will effect upward movement of the piston 4|within the pneumatic cylinder 3l to force a Jet of compressed airupwardly through the nozzle 40 and across the arcing surface of themovable arcing contact 24. This puff of compressed air provides thedesired assistance during the interruption of low-amperage currents tofacilitate upward movement of the arc drawn between the contacts 22, 24upwardly into the extinguishing structure 28. Also, the blast of airthrough the nozzle 48 will tend to effect interruption of the arc drawnbetween the arcing contacts,

It will be noted that, by having the operating cylinder 3l move with theswitch arm 8, a pneumatic means is provided, being very economical inspace. Also, it is to be noted that the fixed relation of the air blastto the contacts always permits the jet of compressed air to beeffectively directed against the drawn arc throughout the entire openingoperation, regardless of the disposition of the movable arcing contact24 and the switch arm 8. Furthermore, by having a relatively shortnozzle fi, there is provided an unimpeded gas-blast passage to hinderthe passage of compressed gas as little as possible.

It is also to be observed that by the construction which f haveprovided, that is, by clamping the pneumatic cylinder 3l to the switcharm 8, the incorporation of my invention may be readily had to circuitinterrupters of conventional design with little alteration. It has beenfound that it is possible to locate the pivot 43 for the lower end ofthe piston rod 42 in such a position that the piston rod 42 practicallycoincides with the axis of the pneumatic cylinder 3l in all positions.

In the modification of my invention as shown in Fig. 2, the constructionis identical to that shown in Fig. i and the operation is the same,except that the pneumatic cylinder 45 is made an integral part of theswitch arm casting 46. By such a construction, the cylinder 45 may beeconomically incorporated with the casting for the switch arm 4:5. Theinternal construction of the pneumatic cylinder 45 is identical to thatset forth in Fig l and the operation is the same. The construction ofFig. 2 lends itself to very economical manufacture.

From the foregoing description of two embodiments of my invention, itwill be apparent that I have provided an improved circuit interrupter ofthe air-break type, in which the interruption of low-amperage currentsis facilitated by the novel pneumatic means set forth. The constructionis readily adaptable to present conventional circuit interrupter designsand is economical in space. It is positive in action, and always insuresa blast of gas toward the arcing contacts to facilitate arc transfer andalso arc interruption. By having the cylinder incorporated with theswitch arm, a single casting need be provided; and, by forming thecylinder of a lightweight material, such as aluminum, the inertia of themoving parts is not materially increased over conventional structures.

The disposition of the nozzle 48 at a fixed distance immediatelyadjacent to the movable arcing contact 24 insures that the blast of gaswill be effectively directed throughout the entire opening operation.

It will be noted that the construction is such that the pneumaticcylinder 3l, 45, is at the same potential as the movable switch arm 8and in any position of operation does not come close to parts at theopposite potential, or ground, and the insulation strength of a poleunit is in no way altered by the addition of this device.

Although I have shown and described specific structures, it is to beclearly understood that the same were merely for the purpose ofillustration and that changes and modications may readily be madetherein, by those skilled in the art, without departing from the spiritand scope of the appended claims.

I claim as my invention:

1. In a circuit interrupter, a relatively stationary arcing contact, aswitch arm, means pivotal- 1y mounting the switch arm adjacent one endthereof, a coacting movable arcing contact carried at the other end ofthe switch arm, a relatively short nozzle carried adjacent the saidother end of the switch arm and directed toward the arcing surface ofthe movable arcing contact, a pneumatic cylinder carried by the switcharm and communicating with the relatively short nozzle, a pistonpositioned within the pneumatic cylinder, a piston rod having oneendthereof connected to the piston, and means pivotally mounting theother end of the piston rod to a substantially xed pivot, the pistonbeing forced through the pneumatic cylinder during the opening operationto send a jet of air through the relatively short nozzle to assist inextinguishing arcing at the contacts.

2. In a circuit interrupter, a relatively stationary arcing contact, amovable switch arm, means pivotally mounting the movable switch armadjacent one end thereof, a movable arcing contact carried by themovable switch arm adjacent the other end thereof, the movable arcingcontact being separable from the relatively stationary arcing contactduring the opening operation of the interrupter to establish an arctherebetween, a pneumatic cylinder carried by the movable switch arm, arelatively short nozzle communicating with the pneumatic cylinder andcarried by the said other end of the switch arm, a piston movable withinthe pneumatic cylinder, a piston rod, means connecting one end of thepiston rod to the piston, means pivotally mounting the other end of thepiston rod to a substantially fixed pivot, and the arrangement operatingduring the opening operation of the interruption to force fluid out ofthe pneumatic cylinder and through the relatively short nozzle againstthe arc to facilitate the extinction thereof.

3. In a circuit interrupter, a relatively station y substantially fixedpivot so that on swinging opening rotative motion of the cylinder thepiston will move within the cylinder to force uid thereout and throughthe relatively short nozzle against the arc to facilitate in theextinction of the arc.

RUSSELL E. FRINK.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 490,762 Bentley Jan. 31, 1893525,332 Card Sept. 4, 1894 1,404,564 Arndt Jan. 24, 1922 2,280,616Baskerville Apr. 2l, 1942 2,399,485 Harlow et a1. Apr. 30, 1946

